Texture Atlas resolution
You could, but I would not recommend it, for these reasons:


Keep in mind that some GPUs out there do not support high
resolution textures.  For instance some older iDevices (and more, but that's off the top of my head).  Blender is very flexible, but some other programs are not.
That is not a power of 2 (the primary reason that we use 1024, 2048,
4096, 8192, etc.), and may not work on some GPUs.  Very bad memory usage.
Texture management becomes really hard.  Versions, overflow from one to another, using layers to keep track of everything, etc.


So my recommendation is to have the textures separated out, still at the 2048x2048.  This allows you to use the GPU efficiently, have good support for GPU RAM, and for instance if you were using GIMP, easily apply filters without having to worry about messing up other parts of the texture.